My suggestions are independent of brand of cable.
Great. Then your suggestions/recommendations should be moot. Please note that we are speaking here of subjective listening impressions, not objective technical measurements.
All else can remain constant. Meaning all gear (amp, speakers, music, volume level, whatever). It could even be conducted in an environmentally controlled room, or not.
Let’s not over complicate matters.
The only thing we need to do with the belden speaker wire is disconnect it from the speakers binding posts, disconnect it from the amps binding post, physically orient the cable in the opposite direction, reconnect to speaker and amp binding posts, play the same music passage and then have clearthink state, “yes, you have reversed the cable” or “no, you have not reversed the cable” and compare that statement to what actually just occurred with the cable. Seems to me he/she should be able to do this 100% of the time, just like if you played Amy Winehouse, then played Bod Dylan and asked if the music changed. It should be that simple and recognizable, according to clearthink (and you, Geoff).